Foods of the Hoary Marmot on Kenai Peninsula, Alaska

Abstract

Plant compositions of the diet and habitat of Marmota caligata were determined on three alpine mountains on the Kenai Peninsula, Alaska, in the summers of 1971 and 1972. Vetches (Astragalus and Oxytropis), sedges (Carex), fleabanes (Erigeron), fescues (Festuca), mosses, lichens (Cladonia),, dryas (Dryas) and willows (Salix) collectively made up about 90% of the overall diet. The 1971 and 1972 diets of marmots were similar for each study area. The marmot populations from different mountains had similar diet-habitat characteristics even though less plant biomass was available in 1972 than in 1971 on two of three alpine study areas. Scant attention has been given to the diet of the hoary marmot (Marmota caligata) or to the plant biomass in the habitats occupied by the hoary marmot. The hoary marmot has been reported to eat mainly green herbage with traces of flowers, seeds and stems (Seton, 1953; Bee and Hall, 1956). Gray (1967) reported the most commonly eaten plants in British Columbia to be: western anemone (Anemone occidentalis), red indian paintbrush (Castilleja), avalanche lily (Erythronoim gradiflorum), blue lupine (Lupinus spp.), wood betony (Pedicularis bracteosa), ragwort (Senecio spp,.), grouseberry (Vaccinium scoparium) and false indian hellebore (Veratrum viride). The objectives of this study were to compare the plant composition of the diet of hoary marmots in three separated alpine mountains and to test for differences between years and habitats. METHODS AND PROCEDURE The study took place on Surprise, Slaughter and Crescent mountains, on the Kenai River drainage near Cooper Landing, Alaska, from late July to early August in 1971 and 1972. Diet composition was determined by a microhistological analysis of recently dropped fecal pellets from each of the three alpine habitats during each summer. Forage species can be recognized in fecal samples by microscopic analysis of the plant cuticle (Storr, 1961; Williams, 1969). Each composite sample of at least 25 fecal pellets was obtained near dens occupied by hoary marmots. It was assumed that the percentage relative density of identified plant fragments is a good approximation for the relative amounts of each plant eaten. Microscope slides were prepared of identified reference plants and fecal samples, as described by Sparks and Malechek (1968), Ward (1970) and Flinders and Hansen (1972). Fields on each microscope slide were viewed at 100 magnifications for identifiable fragments. Twenty fields were examined per microscope slide. The total number of fields examined per fecal sample was 400. Microscope slides were prepared with the number of identifiable fragments per field varying